There have been well-known antibacterial zeolite particles which are prepared by replacing ion-exchangeable metal ions present in zeolite particles with antibacterial metal ions such as silver, copper and/or zinc ions and an antibacterial composition containing the same. In this respect, however, it has been known that an antibacterial resin composition obtained by incorporating such antibacterial zeolite particles into a resin undergoes a color change with the elapse of time. As a means for solving such a problem of color change with time, associated with the conventional antibacterial zeolite particles, there has already been developed a technique in which ammonium ions are incorporated into antibacterial zeolite particles (see Patent Document 1 specified later).
The antibacterial zeolite particles disclosed in this Patent Document 1 would certainly serve as an excellent antibacterial agent and, more specifically, the latter is excellent in the durability of its antibacterial action or power when it is left in air or in water and it never undergoes any quality-deterioration even when it is incorporated into a resin through kneading. The antibacterial zeolite particles are free of any extreme color change under the usual use conditions, but when it is exposed to severe conditions, for instance, it is irradiated with intensive ultraviolet light rays over a long period of time, the zeolite particles suffer from a problem in that it would undergo a color change with the elapse of time. Although the zeolite per se never loses its antibacterial action due to these color changes, a resin product to which the antibacterial zeolite particles are added may often undergo a color change. This in turn results in the considerable deterioration of the commercial value of the resin product depending on the kind thereof.    Patent Document 1: Japanese Unexamined Patent Publication Sho 63-265809